Six healthy male volunteers were exposed to the vapor of 100 and 200 mg of freebase cocaine heated to a temperature of 200 degrees C in an unventilated room (12,600 L volume) for a period of one h. No pharmacologic effects were detected as a result of the exposure. Blood specimens collected immediately following exposure were negative for cocaine and metabolites. Urine specimens contained peak concentrations of benzoylecgonine that ranged from 22 ng/mL to 123 ng/mL by gas chromatography/mass spectrometry. The peak excretion time for benzoylecgonine following passive exposure was approximately five h. The amount of cocaine inhaled by the subjects during passive exposure was estimated from room air measurements of cocaine to be approximately 0.25 mg. The total amount of cocaine (cocaine plus metabolites) excreted in urine by the 6 subjects ranged from 0.04 mg to 0.21 mg. For comparison, the six subjects also received an intravenous injection of 1 mg of cocaine hydrochloride. Four of six subjects screened positive (300 ng/mL cutoff concentration) following the injection indicating that the minimum amount of cocaine in these subjects necessary to produce positive results was approximately 1 mg. A second passive inhalation study was undertaken in which specimens were collected from research staff who assisted in a series of experimental studies with "crack" smokers. The research staff remained in close vicinity while the "crack" smoker smoked three doses of freebase cocaine (12.5, 25 and 50 mg) over a period of 4 h. As a result, staff were passively exposed to sidestream smoke from the "crack" pipe and to breath exhalate from the "crack" smoker. Staff urine specimens contained a maximum of 6 ng/mL of benzoylecgonine. Only traces (<1 ng/mL) of cocaine were detected in any specimen. Overall, these studies demonstrated that individuals exposed to cocaine smoke under naturalistic or artificial conditions absorbed small amounts of cocaine that were insufficient to produce positive urine specimens at standard DHHS cutoffs.